Sirius Passet

[4] A 2022 study suggested that the original preservation mode was phosphatisation that was later altered by low-grade metamorphism with a peak temperature of 409 ± 50 °C (768 ± 90 °F) during the Devonian Ellesmerian orogeny, which resulted in widespread mineral replacement.

[5] Geochemical analysis indicates that the fossils lived close to the boundary of an oxygen minimum zone, possibly being preserved in oxygen-starved periods.

[6] In respect of the importance of the exceptionally preserved fossils in our understanding of the event, the 'Cambrian Explosion in Sirius Passet' was included by the International Union of Geological Sciences (IUGS) in its assemblage of 100 'geological heritage sites' around the world in a listing published in October 2022.

'[7] Although the fauna has not yet been fully described, it is known to consist of a moderate number of arthropods and sponges, and rare representatives of other groups.

It has yielded the problematic taxon Halkieria, and the Panarthropods Kerygmachela and Pambdelurion, all of which have played prominent roles in discussions about the origins of the modern animal phyla.

Location of Sirius Passet during the early Cambrian
Life restoration of Sidneyia inexpectans from the Burgess Shale to which the Sirius Passet form has been considered closely related